Ferromagnetic interactions through control of the bridging geometry

Abstract

A novel trinuclear Ni(II)Cu(II)Ni(II) complex (3) and three Cu(II)Cu(II) (4), Ni(II)Cu(II) (5), and Mn(II)Cu(II) (6) alternating chain complexes were synthesized using the complexed ligand [Cu(bptap)2] (1) which acts as a bis-mer-tridentate ligand (bptap−=2,4-bis(2-pyridyl)-1,3,5-triazapentanedienate). In all complexes, two adjoining metal ions are connected by bptap− in a κ2N:κ3N bridging fashion with local C2 symmetry. The bridging geometry forces the two dσ orbitals directed towards the ligating atoms to orthogonal to each other. Ferromagnetic interaction occurs between Cu(II)Cu(II), Cu(II)Ni(II), and Cu(II)Mn(II) due to the orthogonality of the magnetic orbitals with the magnitudes of J=1.1 cm−1 for 3 (H=−2J(SNi1·SCu+SCu·SNi2)), J=1.4 cm−1 for 4 (H=−2JΣiSCuiSCui+1), and θ=7.5 K for 5 and 1.1 K for 6 (Curie–Weiss model), respectively.